Marking instrument

ABSTRACT

A marking instrument, such as a reservoir pen, has a valve for controlling communication between a reservoir chamber and a feed channel extending through a feed member to a marking tip. The feed member is retractable to open the valve when the tip is pressed against a surface. A subchamber is confined by a diaphragm sealingly connected between the feed member and the barrel, and when the marking tip is lifted from the surface, the diaphragm pushes the feed member forwardly so that the valve closes, after which the volume of the subchamber increases so that the ink is drawn through the channel from the tip.

This invention relates to marking instruments such as writinginstruments of the highlighter pen, felt tip pen, fiber tip pen,ballpoint pen and other types wherein a marking fluid is delivered to amarking tip from a reservoir chamber. The invention is particularlyconcerned with such marking instruments wherein means are provided topressurize the marking fluid in the reservoir chamber to cause the fluidto flow to the marking tip when it is required. In WO 93/05966 forexample there is described a marking instrument wherein the reservoirchamber is partially delimited by a diaphragm, and a member carrying themarking tip is adapted to retract into the barrel of the instrument whenthe tip is applied against a surface so that the diaphragm is deflectedto pressurize the contents of the fluid reservoir. The diaphragm alsoserves as a valve member to isolate the interior of the reservoirchamber from a duct through which the fluid is supplied to the tip whenthe force against the tip is removed and it returns to a forward mostposition. It has been found that under some circumstances, the markingfluid can continue to flow or ooze to the marking tip, especially if thefluid is of a more viscous formulation, when the forces against the tipdue to it being pressed against a surface are released, and this hasbeen observed even where a valve is included to close the communicationbetween the reservoir chamber and the marking tip.

The present invention has for its aim to provide a solution to theproblem explained above and accordingly the invention provides a markinginstrument comprising a reservoir chamber for holding a supply ofmarking fluid, a marking tip for applying the marking fluid to asurface, a fluid supply channel for conducting fluid to the tip,normally closed valve means controlling communication between thereservoir chamber and the supply channel, the marking tip beingretractable to open the valve by pressing the tip against the surface,and means arranged to draw fluid through the supply channel from the tipduring forward displacement of the tip after the valve means has closed.

Conveniently a subchaser of variable. volume is connected to the supplychannel, the volume of the chamber being arranged to increase duringforward displacement of the tip after the valve means has closed. In apreferred construction the subchamber is an auxiliary reservoir for themarking fluid and is partially confined by a resiliently deformablemember which also acts to urge the marking tip to its forwardmostposition. The fluid supply channel is formed in a feed member axiallyslidable in a barrel of the instrument in which the reservoir chamber isenclosed, and the resiliently deformable member is annular and sealinglyconnected between the feed member and the barrel. By this constructionthe resilient member is operable, upon opening of the valve means topressurize the fluid in the main reservoir chamber to effect positivedelivery of the fluid to the marking tip. Furthermore, to simplifyfurther the construction and assembly, the resilient member can define avalve seat of the valve means. Thus, in the preferred embodiment, whichis described in-greater detail below with reference to the drawings, theresiliently deformable member comprises a first collar sealinglyattached to the feed member, a second collar sealingly connected to thebarrel and forming a valve seat, and an annular deformable diaphragmsection interconnecting the first and second collars. The precise formof the valve means is not crucial and it may be of any convenient type,such as a flap valve, or ball valve, having a valve member arranged tobe lifted from its seat by retraction of the feed member and possiblyurged to a closing position by spring means. The volume of thesubchamber or auxiliary chamber need not be very large as fluid issupplied from the main reservoir chamber to satisfy the demand at themarking tip when the valve is opened. However, because the volume of thesubchamber increases after the valve is closed, a negative pressure iscreated and acts to draw fluid back from the tip during the final partof the forward displacement of the tip. As the negative-pressure isgenerated only during a last part of the tip movement, the suctionforces are not so great that air will be sucked into the reservoirsystem, which might interfere with smooth reliable supply of fluid whennext needed.

A more complete understanding of the invention will be gained from thefollowing detailed description of a particular embodiment, referencebeing made to the accompanying drawings, in which:

FIG. 1 is a partial axial cross-section through a marking instrumentaccording to the invention, the components being illustrated in a normalposition when there is no force applied against the marking tip;

FIG. 2 shows the marking instrument of FIG. 1 when the marking tip inbeing pressed against a surface in preparation for laying down a traceof marking liquid;

FIG. 3 shows the instrument of FIGS. 1 and 2 when the tip of theinstrument is being lifted from the surface; and

FIG. 4 is a view similar to FIG. 1 showing a modified construction.

The illustrated marking instrument, e.g. a reservoir pen, has a barrelincluding a body 1 enclosing a main reservoir chamber 2 for storage of avolume of marking fluid, i.e. ink in the case of a pen. The reservoirchamber is of such a kind that its internal volume decreases as the inkis used up. For this purpose the rear end of the chamber can be closedby an ink follower, such as a grease plug, which moves along the chamberto follow the ink column contained in the chamber as the ink isconsumed. In this way it is unnecessary to supply air to the chamber totake up the space vacated by ink as it is used. Of course other forms ofreservoir chamber, such as a collapsible flaccid sack are also possible.Fitted to the forward end of the body is a barrel nose 3 having atapering cone portion leading to a cylindrical forward section 5.Axially slidable in the nose section 5 is a feed member 6 consisting ofa cylindrical rod or bar with an axial bore 7 forming an ink supplychannel for conducting ink to a marking tip 22 carried at the forwardend of the feed member. The marking tip's particular type forms no partof this invention. The tip can be, for example, a felt tip, a fiber tip,ball point, roller ball, tubular nib or any other tip commonly used inmarking instruments equipped with liquid reservoirs. At its trailing endthe feed member 6 has a portion of reduced external diameter and seatedagainst the annular shoulder defined on the feed member is a forward orinner collar 9 of a resiliently deformable member of which in theillustrated embodiment takes the form of a bellows-like diaphragm member8. This diaphragm member includes a rear outer collar 10 which is sealedto the barrel and is hold clamped against the forward end of the body 1by a sleeve 11 inserted between the body 1 and the nose 3. The inneredge of the collar 10 has a radius greater than that of the trailing endportion of the feed member and defines a valve seat for cooperation witha valve member in the form of a ball 12. The combination of valve seatand valve member constitute a normally closed valve means which controlscommunication between the reservoir chamber 2 and the ink supply channel7. Extending between the collars 9, 10 of the diaphragm member is aresilient, deformable, rearwardly divergent bellows portion 13. Theresilience of the diaphragm member 8 acts to urge the feed member 6, andhence the writing tip, to a forwardmost position and when in thisposition the diaphragm member encloses, with the trailing end of thefeed member and the valve ball 12, a small volume subchamber 20 whichcommunicates with the ink feed channel 7 through radial ports 14 in thefeed member. The valve ball 12 is biased forwardly into sealingengagement with the seat by a coil spring 15 which is supported by aspring support 16 of cruciform cross-section having slots in the wingsthereof to accommodate the spring.

In the normal rest condition illustrated in FIG. 1, the trailing end ofthe feed member is spaced at a small distance from the valve ball whichis held in sealing engagement with the valve seat thereby isolating themain reservoir chamber 2 from the subchamber 20 and the feed channel 7.Upon applying the writing tip against a surface 24 under normal writingpressure, the feed bar 6 retracts into the barrel and its trailing endfirst takes up the clearance between the feed member and the valve ball.This initial retraction causes the bellows portion to reduce the volumeof the subchamber to pressurize the liquid contained in the subchamberto displace the liquid into the supply channel for delivery to thewriting tip. Upon further retraction the feed member lifts the ball awayfrom its seat against the bias of the spring 15, whereby communicationbetween the main reservoir chamber 2 and the subchamber is established.As the retraction of the feed member continues the bellows portion 13 ofthe diaphragm member collapses inwardly further reducing the volume ofthe subchamber 20 and pressurizing the ink contained in the reservoirsystem to force the ink to flow through the feed channel 7 to thewriting tip. This is the condition illustrated in FIG. 2. When thewriting tip is subsequently lifted from the surface, e.g. at the end ofwriting a word, the diaphragm member 8 urges the feed member 6 forwardlyand its bellows portion 13 expands again. The resulting increases involume of the subchamber 20 is initially satisfied by ink passing fromthe main reservoir chamber 2 through the still open valve. Upon thevalve closing however, a small amount of the forward stroke of the feedmember still remains, and the increase in volume of the subchamber whichoccurs during this part of the stroke results in a negative pressurebeing created in this space 20 tending to draw ink back through thesupply channel from the tip, as shown in FIG. 3. In this way excess inkis prevented from accumulating at the writing tip when the tip is liftedfrom the surface being written on, but as soon as the tip is appliedagainst the surface again ink is supplied to the tip to avoid any riskof ink starvation at the tip. By restricting the drawing back of ink tothe end part of the forward displacement of the feed member there isavoided any risk of air being sucked into the pen and interfering withthe smooth operation of the ink supply system.

It will be appreciated that the level of suction obtained in thesubchamber 20 after the valve has closed will depend on the shape of thebellows and the forward movement of the feed member after valve closure,and by selecting the bellows profile and clearances the suction affectcan be adjusted.

Modifications to the construction of the reservoir pen described aboveare of course possible without departing from the scope of the claimswhich follow, and an embodiment incorporating some such modification isillustrated in FIG. 4. Instead of a ball, it has a valve member 12' witha frustoconical surface arranged to cooperate with the valve seat,whereby a larger valve opening is obtained for a given displacement ofthe valve member, which may be desirable if a viscous ink is being used.The valve member 12' is slidably guided in the pen body 1 by several,e.g. eight radial projections spaced apart around the valve member.Rather than discrete ports 14 connecting the subchamber 20 with the inksupply channel 7, this communication is established through a pair ofdiametrically opposed slots 14' which extend longitudinally from therear end of the feed member 6. The extended ports defined by these slotsmay provide improved ink flow characteristics. In order to provide amore positive location of the forward collar 9 of the diaphragm member8, the feed member is provided with a circumferential groove in whichthe collar is seated. Other modifications will occur to those skilled inthe art.

We claim:
 1. A marking instrument comprising a reservoir chamber forholding a supply of marking fluid, a marking tip for applying themarking fluid to a surface, a supply channel for conducting fluid to thetip, normally closed valve means controlling communication between thereservoir chamber and the supply channel, the marking tip beingretractable to open the valve means by applying the tip against thesurface, wherein means, separate from the valve means, are provided todraw fluid through the supply channel from the tip during forwardmovement of the tip away from the valve means after the valve means hasclosed.
 2. A marking instrument according to claim 1, wherein the valvemeans includes a subchamber of variable volume which is connected to thesupply channel, the volume of the chamber being arranged to increaseduring forward displacement of the tip away from the valve means afterthe valve means has closed.
 3. A marking instrument according to claim2, wherein the subchamber is partially confined by a resilientlydeformable member which acts to urge the tip forwardly away from thevalve means.
 4. A marking instrument according to claim 3, wherein theresiliently deformable member defines a seat of the valve means.
 5. Amarking instrument according to claim 3, wherein the supply channel isformed in a feed member axially slidable in a barrel of the instrument,and the resiliently deformable member is annular and sealingly connectedbetween the feed member and the barrel.
 6. A marking instrumentaccording to claim 5, wherein an inner end of the feed member isarranged to act on a valve member of the valve means for opening thevalve means.
 7. A marking instrument according to claim 2, wherein thevolume of the subchamber diminishes during retraction of the tip afterthe valve means has opened for pressurizing the contents of thereservoir chamber for delivery of fluid to the tip from the reservoirchamber.
 8. A marking instrument comprising a barrel enclosing areservoir chamber for holding a supply of marking fluid, a feed memberaxially slidable relative to the barrel and carrying a marking tip at aforward end thereof, a supply channel extending through the feed memberfor conducting fluid to the tip, an annular resiliently deformablemember sealingly connected between the feed member and the barrel andconfining a subchamber communicating with the supply channel, anda-normally closed valve means, separate from the deformable member,controlling communication between the reservoir chamber and thesubchamber, the marking tip being retractable to open the valve means byapplying the tip against a surface.